Conventionally, there are heat supply systems that allow a plurality of heat utilization devices, such as a hot water supply device or an indoor heating device, to utilize heat generated by a plurality of heat source devices. For example, in a heat supply system described in Patent Document 1 (JP 2013-104596A), warm water in which heat generated by a plurality of heat source devices, namely a heat pump and an external heat source, has been recovered is supplied to a plurality of heat utilization devices, namely a hot water storage tank and an indoor heating device, while flowing through a water circuit and warm water circuits.
In the heat supply system described in Patent Document 1, a priority rank when operating the heat pump and the external heat source is set in advance. Also, the heat pump and the external heat source are operated in the order of that priority rank according to a load state.